Light control



Feb. 17, 1931.

saueci 5 F. MICHELSSEN LIGHT CONTROL Filed March 21, 1927 DEXTROROZ4RY 0/001 CRY-5713f (A'VOKOMRY cRYsru INVENTOR Ff/TZ MIC/112685 4 MQdW TORNEY Patented Feb. 17, 1931 FRITZ .MIUHELSSEN, OF BERLIN, GERMANY, ASSIGNOR T GESELLSOHAFT Flllt DRAET- LOSE TELEGRAPHIE M. B. H. HAL-LESGHES, 01" BERLIN, GERMANY, A CORPORATION OF GERI/IANY LIGHT CONTROL Application filed March 21, 1927, Serial No. 177,204, and in Germany March 23, 1928.

A method for controlling light which is based upon the theory of passing polarized light through an anisotropic substance, and causing the latter to start vibrations for controlling purposes, is known.

I is associated with an action upon the polarized condition of the light which, in well-known manner, is used for altering the intensity of the light issuing from an analyzer. The phenomenon of influencing the state of polarization of light by a vibrating crystalline substance or material is based both upon double refraction as well as upon rotational dispersion of the light, and it has been found that this latter phenomenon of rotational dispersion influences the intensity of. the issuing light. This influence on the kind of the light is undesirable in many cases, for instance, where the transmission of fluctuations in the brightness of white light is concerned, for on accountof rotational dispersion it is then impossible to obtain complete darkness by crossed Nicol lenses.

In my present invention I have disclosed an arrangement by the aid of whichit is pos: .sible to neutralize and obviate the undesirable action otrotational dispersion. With this end in view, a second anisotropic substance is disposed in the path of the rays of light which are passed through the anisotropcsubstance that is caused to vibrate as, for example, an arrangement as disclosed by Alexander Meissner in Serial No. 117 ,583, filed February 28, 1927, with the result that the color dispersion of the light occasioned by the first sub.- stance is re-compensated'by the second 'anisotropic body. For example,'if the crystal- 1 line or .piezo-electric material through which polarized li ht is passed from a light source and which, y electric oscillations, is caused to vibrate at its natural period, consists of a 1 dextrorotatory quartz crystal or, in other words, a crystal having a clockwise rotational "effect, then, according to this invention, a levorotatory quartz crystal or one to produce a counter-clockwise rotational effect. is

disposed ahead of the former, with the result mutual compensation of the anisotropy of the This method two crystals is produced. it, then, one of the two quartz crystals is excited, the penetrating luminous rays after their passage through the second quartz crystal will be influenced only by the action of the double refraction due to the oscillations, whereas the phenomenon of rotational refraction is eliminated.

The arrangement hereinbefore disclosed is of especially great importance in connection with picture telegraphy and television.

The fundamental idea of this arrangement, without going here into details regarding the physical phenomena occurring within the crystalline material, is, therefore, that of passing the light rays through both an eX- cited crystal and a second similar crystal, the latter, however, being of such a nature that it compensates for the color dispersion caused by the former crystal. When in uneXcited state, the two crystals thus constitute, as it were, one anisotropic body.

The accompanying drawing shows diagrammatically one form which my arrangement may assume.

Referring now to the drawing, I have indicated the light source by the numeral 1 and light projected from the source is then passed through a lens 3 anda diaphragm 5 so as to strike a Nicol prism 7. The Nicol prism 7 polarizes the light from the source 1 in one plane and this plane polarized light beamis then passed through a crystal 13 which has dextrorotatory power. Electric current potentials are supplied to the crystal 13 by means of electrodes 15 and 17 connected b conductors 39 and 37 respectively to the osci latoyy circuit 25 which is coupled by means of a transformer to a vacuum tube system 27. Signal pulses may be applied across the resistance 29 and the capacity 31 by connecting the same to the terminals 33 and 35.

After the electric potentials have been applied to the electrodes 15 and 17 of the crystal 13, the plane polarized light beam passing;

therethrough from the Nicol prism 7 is doubly refracted'or elliptically polarized and is then passed through a second crystal 1 9 of similar pro erties to the crystal 13 except for the act that the crystal 19 has levorotatory power and compensates for light directing dispersion occasioned by light beam passing through the crystal 13. The crystal 19 is referably supported by ,supporting mem bers 21 and 23, and lig t after leaving the crystal 19 is then passed through a second Nicol prism 9 which may be termed an analyzer in that the plane polarized beam as issuing from the Nicol prism 7 is polarized in a plane at right angles to the first plane of polarization and whatever light passes beyond the Nicol prism 9, in accordance with the potentials on the crystal 13, may be recorded upon the screen l'lin any desired manner.

Having thus described my invention, I am entitled to all modifications as fall fairly within its spirit and scope as defined by the appended claims, wherein I claim:

1. In a light control system, a piezo-electric' body permeable to ligoot, a lightsource for I light tosaid dy, means associated with said body for controlling the amount of light passing throu h said body, and acrystal in the path of t e light issuing from said pie'zo-electric body for compensating for color dispersion produced in the light issuing from said piezo-elect-ric body.

2. In a light control system, a light source, an electro-mechanical vibrator for controlling the light issuing from said source, and a light permeable crystal in the path of the controlled light issuing from said electromechanical vibrator for compensating for color dispersion produced in the light ,issuing from said electro-mechanical vibrator.

3. In a light control system, a light permeable crystal, a lightsource, means for directing polarized light to said crystal, means for controlling the polarized light passing through said crystal, and a second light permeable crystal in the path of the light rays issuing from said first crystal for compensatin for distortional errors produced in said rst crystal.

4. In a light control system, a light permeable crystal, a source ofjight, means for polarizing the light issuing from said source,means for directing said polarized light through said crystal, means associated with said crystal for doubly retracting said polarized light passing therethrough, a second permeable crystal in the path 0 the said doubly refract- .with said vibrator for supplying a varying frequency thereto whereby the said directed light is varied in proportion to the supplied frequency by doubly retracting said light passing through said vibrator, and a crystal in the path of the light issuing from said crystalline vibrator for compensating for color dispersion produced in the light issuing from said crystalline vibrator.

6. In a light control system, a light source,

an electro-mechanical vibrator, a light polarpath of the controlled rays of said crystal for polarizing the light issuing therefrom in a plane at right angles to the plane of polarization of said first polarizer whereby in the absenceof oscillations on said vibrator no light will pass said second polarizer.

7. In a light control system, a light permeable crystal, a source of light, means for polarizing said light and directing said polarized light through said crystal, means for vibrating said crystal to control the plane ofpolarizationiof said light, said means introducing color dispersion in the light pamin'g through said crystal, and a second crystal isolated electrically from any source of electromotive force in the path of the light is-' crystal. 7

FRITZ MICHELSSEN.

1 ed light issuing from said first named crystal for compensating for color dispersion produced in the light issuin from said first named crystal, and means or polarizing the compensated light beam issuing from said second named crystal in a plane at right angles to the lane of polarization of said first named p0 arizing means.

5. In a light control system, a light source, a crystalline vibrator inthe path of the light issuin from said source, means for directing an controlling the light passing through said yibrator, means associated 

